Because　of　its　inherent　drawbacks,　the　conventional　AC　power　meter　method　for　magnetics　core　loss　has　been　limited　in　some　case.　A　new　method　based　on　testing　the　input　power　difference　with　and　without　the　DUT　core　in　the　circuit　is　proposed　and　it　is　called　as　differential　method　in　this　paper.　The　new　method　eliminates　the　problem　of　high　errors　with　AC　power　meter　method　due　to　the　phase　shift　error　in　the　condition　of　high　frequencies　and　high　DUT　impedance　angles.　Its　suitable　applications　are　described　and　analyzed　deeply.　The　test　scheme　and　circuits　are　also　presented　which　is　especially　appropriate　for　the　core　loss　tests　with　low-frequency　current　bias,　such　as　in　the　PFC　inductors.　Measured　results　verify　the　accuracy　of　the　technique　by　calorimetric　method.　©　2014　IEEE.